Modélisation et étude expérimentale du soudage par induction de composites thermoplastiques

Abstract

The use of high performance thermoplastic composite material increases more and more. It is therefore relevant to study in depth their joining processes and to determine the parameters allowing good mechanical performance. This study focuses on induction welding but also gives an overview of resistance welding and ultrasonic welding. These three welding processes were identified in the literature as the most promising ones. A three dimensional finite element model of the induction welding of carbon fiber/polyphenylene sulfide (CF/PPS) thermoplastic composites is developed using the Comsol Multiphysics® software. The model takes into account a stainless steel mesh heating element located at the interface of the two composite adherends to be welded. This heating element permits to localize the heating where it is needed most, i.e., at the weld interface. The magnetic, electrical and thermal properties of the CF/PPS and other materials are identified experimentally or estimated and implemented in the model. The model predicts the temperature-time curves during the heating as well as the temperature distribution over the weld area. Furthermore, a sensibility analysis is developed with the aim of identifying the parameters and properties that have the greatest effect on temperature. These are input current, frequency, distance between coil and joint and adherend electrical conductivity. The first three parameters are easily controlled and the last one must be identified with good accuracy. The effect of the heating element size and input current on the thermal behavior is investigated, both experimentally and using the developed model with four different heating elements and three input currents. The welds quality is assessed through microscopic observations of the weld interfaces, mechanical testing and observations of the fracture surfaces. A heating rate of 5°C/sec and a ratio of the open gap area on wire diameter of the heating element of 14 lead to a good weld quality. A higher heating rate leads to more porosity at the weld line. A comparison with resistance welding and ultrasonic welding was carried out and showed similar joint mechanical performance, indicating that that the welding process selection should be based on other parameters such as the joint geometry.

Date	11 Dec 2014
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Martine Dubé (Supervisor)